The present invention relates to die ovens, and more particularly to single cell die ovens.
Metallic extrusion is a popular method to produce a variety of products. In a typical extrusion, a hot metal billet is placed in a hydraulic press and squeezed at high pressure through a preheated die. The metal emerges from the die in the desired cross section.
The preheating of the die is critical. If the die is too hot, the life of the die may be shortened. For example, if it is too cold, the quality of the extruded metal will not be satisfactory or the die may even break. A die for aluminum extrusion should be preheated to a temperature in the range of 800 to 900 degrees Fahrenheit before the die is used.
Die ovens are often used for preheating the die. Single cell die ovens preheat one die. By locating one or more single cell die ovens near the press, the efficiency of the operation of the press is increased. Infrared heating elements or electric heating elements are used in the single cell die ovens to decrease the amount of time required to preheat the die.
Infrared die ovens heat the die much faster than a conventional die oven. Because the die is heating much faster, precise control of the die temperature is difficult. Additionally, when the infrared heating elements are initially energized, the amount of heat generated will ramp up. When the infrared heating elements are turned off, the heaters will ramp down.
If the size and temperature of the die is known when the die is placed into the oven, experimentally derived or calculated die heating curves can be used to determine the amount of time required to preheat the die. After the amount of time for heating the die has lapsed, temperature sensors measure the temperature of the air in the oven. A controller then maintains the air temperature inside the oven at a desired level.
The problem with such a solution is obvious. The oven operator has to insure that each die placed in the oven is of correct size and temperature and that the correct heating curve is inputted to the control system for that die. This increases the complexity of operating the die oven and increases the possibility of improperly heating the die. For example, if a die is removed from a press for service to the press, the die must be allowed to cool to room temperature before being preheated in the die oven. If not, the die could be heated to a temperature which would structurally or materially damage the die.
An improved single cell oven which is flexible allowing for the use of dies of different size and temperature is thus highly desirable.